Cheese whey is a by-product from the production of cheese. This whey is generally used as a raw material for whey protein or lactose, or used as a raw material for improving the taste of bread or baked sweets, as a raw material for beverages, or as a raw material for infant formula or the like.
However, when whey is used as a raw material for infant formula, because the whey includes large amounts of minerals, there are limitations to the potential applications of the resulting formula.
Generally, in order to achieve a composition similar to human breast milk, infant formula is produced with a protein content of 9.5 to 11 g and a phosphorus content of approximately 6.8 mmol per 100 g of powder. Furthermore, the composition of the protein within the formula is typically set to 40% casein and 60% whey protein in order to achieve a similar composition to human milk.
Many minerals including phosphorus in high purity whey protein isolate or whey protein concentrate are demineralized, and because of their protein content and phosphorus content, have a composition that enables their use in bringing the composition of infant formula closer to that of breast milk.
However, research is still being conducted into trace nutrients derived from human milk that are particularly important for newborn infants, and as far as possible, it is considered desirable to use formulas which, while using cheese whey or other milk-derived raw materials that retain the trace nutrients derived from milk, have undergone removal of components such as phosphorus that can exist in excessive amounts for infants.
For example, provided acid casein (casein: 84%, phosphorus: 23 mmol/100 g) is used as a casein source, then the casein content can be readily controlled, but it is preferable that, as far as possible, skim milk powder (casein: 27.2%, whey protein: 6.8%, phosphorus: 31 mmol/100 g) is used, with whey used, where possible, as the source of the whey protein.
In this case, the whey includes phosphorus in an amount of 18 to 22 mmol/100 g solids, and this phosphorus content must be reduced to not more than 6 to 12 mmol/100 g solids. Accordingly, the development of techniques that enable infant formulas to be brought closer to the composition of human breast milk, while reducing the phosphorus content within the whey, is very important.
One technique for reducing the phosphorus content within a whey is an ion exchange resin method (for example, see Non-Patent Document 1).
Further, known methods for manufacturing low-phosphorus whey include (A) methods that use only an ion exchange resin (for example, see Patent Document 1), (B) methods in which demineralization is first performed using an electrodialysis membrane or nanofiltration (NF) membrane or the like to reduce the demineralization load on the ion exchange resin, and the partially demineralized whey is then passed through a strongly acidic cation exchange resin and a strongly basic anion exchange resin (for example, see Patent Document 2), or (C) methods in which the whey is first passed through a cation exchange resin in hydrogen form and an anion exchange resin in chloride form, and is subsequently subjected to electrodialysis or nanofiltration (for example, see Patent Document 3).
In the method disclosed in Non-Patent Document 1, the whey is first passed through a cation exchange resin that has been regenerated in hydrogen form, thereby substituting the metal cations with hydrogen ions and causing an acidic eluate to be discharged from the exchange resin. Subsequently, this eluate is passed through an anion exchange resin that has been regenerated in hydroxide form, thereby substituting the anions (citrate, phosphate, chloride or lactate) with hydroxide ions to effect demineralization. This method is capable of achieving a high demineralization rate of 90 to 98%.
In the method of manufacturing low-phosphorus whey protein disclosed in Patent Document 1, a whey protein concentrate having a protein content of 70% by mass is diluted, and the pH of the diluted solution is adjusted to 4 or lower. Subsequently, the solution is brought sequentially into contact with a cation exchange resin in H+ form and then an anion exchange resin, thus yielding a low-phosphorus whey protein in which the phosphorus content has been reduced to not more than 0.15 mg per 1 g of protein.
Patent Document 2 relates to a method of concentrating and demineralizing a cheese whey, and in an Example 4 within this document, high-protein substances are removed from a skim acid cheese whey solution by ultrafiltration, and a reverse osmosis membrane having a particularly low salt rejection rate is then used to perform concentration and demineralization simultaneously. Subsequently, the obtained whey concentrate is passed through a strongly acidic cation exchange resin and a strongly basic anion exchange resin of a mixed bed ion exchange apparatus to complete demineralization.
In the method disclosed in Patent Document 3, a concentrated whey is first introduced into a weakly cationic or carboxylic acid column to achieve ion exchange of 60 to 70% of the divalent cations with protons, and ion exchange of 5 to 15% of the monovalent cations with protons. Subsequently, the resulting eluate is introduced into a mixed bed column containing a strong cation exchange resin and a strong anion exchange resin, thereby exchanging the remaining calcium ions and magnesium ions with protons. Moreover, the sodium and potassium ions are also exchanged with protons, and sulfate anions undergo ion exchange with chloride ions, yielding a strongly acidic (pH 2 to 2.5) eluate. This eluate is introduced into an electrodialysis apparatus, and the majority of the chloride anions and the majority of the protons are removed. The resulting product is then passed through a strong anion exchange resin to exchange citrate ions and phosphate ions with chloride ions.